First, a necessary bit of boilerplate. If you see something that looks very like this mod being offered for sale, be aware that someone who isn't me may be trying to get you to buy pirated (and unsupported) goods and you should avoid them. It might be nice to tell me about it, though :)

And now, about the mod itself. Have you noticed that some NPCs are clearly meant to be elderly if you look at their faces, but their bodies seem to be more appropriate for a younger person? Furthermore, this is not consistent - some older NPCs have bodies and faces that match.

Now, this may or may not bother you, but the visual disparity annoys me. What most people might have done is make the fake-old NPCs younger. Instead, I reckoned that generally the NPCs are supposed to be the age their faces look, so decided to make their bodies match their faces.

Versions 1.1 and later are much more compatible with other mods, as I've been able to use TESVGecko and TES5Edit to get rid of the race edits, leaving just the NPC edits. This also makes the plugin much, much smaller.

I keep this mod synchronised with the Unofficial Skyrim Legendary Edition Patch (USLEEP), but do not require that you use USLEEP. As of version 3.1 this means that there are USLEEP and non-USLEEP variants of this mod - please make sure you use the version appropriate for your load order.

NOTE: This mod is completely agnostic about body mesh and texture replacer mods such as CBBE/UNP/Sundracon/FavoredSoul/SoS/Whatever. It contains no body mesh or texture replacers itself, it just applies whatever textures are being used for old people in your game to more of the NPCs. If you are seeing issues (ankle seams with UNP seems to be a popular one) then this mod is not the cause - what is happening is that whatever body mod you are using already has problems with older people, it's just that with this mod those problems are more noticable because more NPCs are using the older person body textures.